Process of catalyzing gaseous reactions



Patented Dec. 23, 1924.

UNITED STATES PATENT-OFFICE.

MARVIN PIPKIN. 0F FO'RT-MEADE, FLORIDA.

i g PROCESS or CATALYZING GASEOUS REACTIONS.

No Drawing.

To 077 whom it may concern:

Be it known that I, MABvIN Piriux, a 'citizen of the. United States, residing at Fort Meade, in the county of Polk, State of Florida, have invented certain new and useful Improvements in Processes of catalyzing ('i'aseous Reactions, of whichthe following is'a specification. v

I have discovered that-activated charcoal is an excellent catalytic material for accelerating reactions between gases. Further, I have found that the catalytic properties of the activated charcoal can be greatly ac. elerated by impregnating the same, with .a metal, metallic oxide or mixtures of the same by my" improved process.

Activated charcoal. 1's charcoal which has been treated at elevated temperatures with an oxidizing gas'which has the capacity of reacting with the charcoal to remove ,a IP21"- itiOnalpbrtion of the samefrom within its structure, thus leaving the resultant char 1 highly porous and possessing a large amount of c'arbon surface. The large surfaces of the activated charcoal then-become contactingfsurfa'ce's for the gases. It is probably.

due to the extremely large surfaces available "for contact thatthe activated carbon possesses its high catalytic value-.-

By bringing a mixture of gases at the appropriate temperature in contact with acti-' valed charcoal, I am able to cause reaction I i of thegases to form new products. The

temperature best adapted for reaction 18 specific for each gaseous mixture. In gencral it may be stated that as low a temperature as possible is used, provided a satisfactory yield of product is obtained. .High

pressures frequently are used to increase the concentration of reacting gases, the precise pressure being regulated in accordance with each specific reactlon.

lhe following example lllustrates an appl cation of my invention:

Example I: A gaseous mixture of oxygen and nltric oxide 1n the proportion of one volume of oxygen to two of oxide of nitrogen is passed thru activated charcoal" which is-being cooled, thus maintaining a temperature below the kindling point of the activated charcoal, the temperature of 150 C. being satisfactory The mixed gases in passing thru the activated charcoal unite to form nitrogen dioxide N0 The nitrogen dioxide isthen passed into water, producing a mixture of nitric and nitrous acids.

oxide.

Application filed September 29, 1921. Serial No. 504,228..

Upon heating the nitrous acid, nitric acid is produced and nitric oxide generated. This nitric oxide is passed back thru the system again for conversion into'nitric acid. The nitric acid is concentrated to any dcsirable concentration or converted into salts by neutralization with alkalies, and the salt solution evaporated to a solid state in ac cordance with the requirements.

For certain purposes have found that metals" or metallic oxides can be incorporated internally in the carbon, such process being termed impregnation, and to accomplish this purpose the following method has been found especially desirable. The method is economical to perform and simple in operation. A decomposable salt of the metal and oxide of the metal to be impregnated is dissolved in water, and the solution added to the activated carbon. In certain cases the decomposable salt can be added to the activated carbon as such in the form of a mixture with the latter or can be incorporated with the activated carbon by fusion of the salt with the activated carbon. The concentration of the solution used and the quantity of the solution added are regulated in accordance with the percentage of metal or oxide desired in the activated carbon. The water is then removed by evaporation, and after such drying the material is heated to or above the decomposition point oi the coinpound'used. In many cases the drying and the decomposing can be accomplished simultaneously. If the oxide is reducible by carbon at the temperature of decomposition mentioned above, then the activated carbon will be impregnated with metal. If, however, the oxide is not reducible by carbon then the resultant product is activating carbon' impregnated with the oxide. In general, heating with carbon in the absence of air tends to give the metal, and heating in the presence of air tends to produce the Conditions are regulated accordingly, depending upon the roduct desired.

The'following example il ustrates the applicability of the above:

. Example II: Activated carbon is treated with a solution of co per nitrate. The

amount of solution use is just suflicient to fill the pores of the carbon and moisten the surfaces. The material containing the carbon and copper nitrate solution adsorbed therein is then heatedto evaporate the water, leaving the copper nitrate with- Heatin'g is continued thcn to'a tcn'iperatu're nated into activated carbon by of approximately-"500 C. to decompose the copper nitrate. all'being accomplished in a' single operation. Thirty Illl I1 UtS"SllfilCG :for the treatment to give La satisfactory product. The materia'his cooled out of contact with air. and the'resultant material ls'ttt'tlvtltttl charcoal. nupregnatednnth metallic, copper. It it is desired-to obtain Impregmitcd copper ox1de;. '1t 1s necessary to roast and calcine in the presence of air or some other oxidizing substance, in which case. cooling in contact with air is allowable, provided the temperature of the material upon discharge into the air is not sufiiciently great to 7 cause the carbon to burn. By proper regulation of the degree of heating and air supply a mixture of metallic copper and copper oxide impreg-v nated into the activated carbon is obtained.

Among other metalsand oxides which are adapted to this modification of my invention are 1ead,'zinc,'silver, cadmium. iron, nicke'h'mercury andbismuth. Among other oxides of metals which cannot be reduced by carbon, but Which can be impregthis method, aremanganese, chromium and aluminum. By my treatment such compounds as sodium zincate and potassium dichromate can be impregnated into activated carbon so that the final product: in each case contains two different metallic oxides or a metal with an oxide of another metal. The above metals are typical of a large number which may be .used in like manner. Such impregnated materials when they contain an oxidizing agent such as potassium dichro- 2 mate, are valuable for, the oxidizing pow-j er of the oxidizing, agent acting'onthe adsorbed gases. Likewise the adsorbedmetallic oxides in certain cases function as oxi dizing agents on the adsorbed gas. 'Iinpregnated metal products function ordinar rily as reducing agents, or as catalytic pro-f .n'ietal.

"actions by contacting (luring surfaceslor increasing the catalytic power. ota theactivated charcoal."

As-a'spc'cialuse for in'ipregnating car,- bon' I would mention carbon impregnated with copper and its use in removing arsine and phosphinc by oxidation'vwhen such are present in a mixture of gases containing 'suflicient oxygen to combine. with the ihosphine and arsiue when passed thru coppcr nnpregnntcd activated charcoal. Also this material has great value tor remoi ingsuch gases as phosgcnc CUP-l. as

Well as other gases used in chemical Warv fare. and as such find specific application.

My inyention is broad in its sc pe both as to materials impregnated n the activated preparing and using the same. and in this 'rclatioir'thc examples give i' above are; only illustrative of the scope of my -i n\' 'i,ition. said scope being limited only in this :rcspcct to thetollowing'claims.

I claim as my invention:

".1. The process of catalyzing gaseous reactionshy contacting gaseous mixtures with activated carbon :at pressures greater than atmos 'iheric pressure.

2. The. process. of producing gaseous reactions by contacting gaseous mixtures with activated carbon impregnated with a 3."The process of producing gaseous re actions by contacting. gaseous mixtures metallic oxide,

4. Theprocess ot/prod ucing gaseous re 7 gaseous mixtures with carbon impregnated with an vwith activated carbon impregnated with a activated oxide.

/ .f 5. The-process pf pi oducmg gaseous reactiyins by contacting gaseous mixtures with activatedcarbon impregnated with a mixture of metal and oxide.

Intestimony/whereof, I afiix my signature. l,

/1 /MARVIN PIPK-IN.

charcoal and as to the general methods of 

